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Resolving Shocks Around Galaxy Clusters with GLAST

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  1. Resolving Shocks Around Galaxy Clusters with GLAST Avi Loeb, Harvard University Collaborators:Eli Waxman, Uri Keshet

  2. Structure Formation in the IGM Density contrast of gas at z=0 for a 100x100x10 Mpc^3 slice Density contrast of gas shocked between z=0.14-0.09

  3. Collisionless Intergalactic Shocks For a shock compression factor For strong shocks: Examples: SN 1006, SN RX J1713.7-3946 E_max= 100 TeV (from X-ray and TeV observations) v_sh ~ 1000-2000 km/s Energy fraction in relativistic electrons:

  4. IGM Acceleration Parameters Larmor radius = the magnetic field could have a short coherence length. The acceleration e-folding time: Cooling time: Maximum Lorentz factor: Scattered CMB:

  5. Spectrum of Scattered Radiation 10-15% In young X-ray clusters: virialization shock infall cluster But note that if r~2 instead of 4:

  6. Gamma-Ray Background T=1 keV strong shocks Simulations T=0.3 keV strong +weak shocks Loeb & Waxman, Nature, 405, 156, 2000

  7. Cosmic Background Radiation Gamma-ray background

  8. 3C279 Cygnus Region Vela Geminga Crab PKS 0528+134 LMC Cosmic Ray Interactions With ISM PSR B1706-44 PKS 0208-512 EGRET All Sky Map (>100 MeV)

  9. fewer free parameters: only ξe and ξB Weak shocks (mergers + accretion) Complicated 3D geometry Additional physics (preheating, feedback) (GADGET; Springel & Hernquist) SPHsimulation 2243~107 gas / dark matter particles 200 Mpc box, Z0=50 ΛCDM cosmology ΩΛ=0.7, Ωd.m.=0.26, Ωb=0.04 H=0.67, k=0, n=1, σ8=0.9 Cosmological Simulations Motivation: Springel & Hernquist (2000)

  10. >10 GeV Δθ=12’ Z=0.012 1015M⊙ >100 MeV γ-ray images Δθ=42’ Targets for MAGIC, HESS, VERITAS Keshet et al. (2003)

  11. Gamma-Ray Clusters Flux Above 1 GeV From a Simulated 16x16 degrees^2 Field EGRET GLAST Keshet et al. 2001

  12. Number Counts at 100 MeV From Simulations Keshet et al. (2002)

  13. Radio Clusters A2163 Feretti et al. 2001

  14. Radio Surface Brightness Govoni et al. 2001

  15. Model: Lν (T)∝T 7/2 Diffuse radio sources Best fit: Best fit calibrated model Radio halos: association with structure formation Keshet, Waxman & Loeb (2004b)

  16. Predicted Anisotropies Press-Schechter+self-similar accretion onto X-ray clusters Waxman & Loeb, ApJL,545, L11 (2000)

  17. “Accelerator Beam Dump” for collisionless shocks in galaxies Ultraluminous Infrared Galaxies (ULIRGs): Factories of High-Energy Neutrinos • ULIRGs discovered by IRAS in mid 80’s • LFIR > 1012 L>> Loptical (dusty) • Disturbed Morphologies: Mergers • Powered by nuclear starbursts&/or obscured AGN (much debated) • Key phase in growth of elliptical galaxies and massive black holes

  18. Physical Conditions: Arp 220 Radio Emission; FIR-Radio Correlation + Radio SN  ~ 100 pc scale starbursts with ~ 100 M/yr Condon et al. 1991 Individual Radio SN detected w/ VLBI The collisionless shocks of SNe are likely to inject relativistic electrons and protons (cosmic-rays) into their dense gaseous environment 1” = 350 pc Smith, Lonsdale, Diamond

  19. Fate of Injected Cosmic-Rays • The energy loss time of a relativistic proton • The starburst lifetime (a few dynamical times) • SN injected protons will dissipate all their energy if Matches the minimum surface density of starburst galaxies!

  20. Injection of relativistic e- & p+ • Synchrotron cooling time of e- is much shorter than e- escape time (Thompson et al. 2006). • Proton-nucleon loss time is much shorter than cosmic-ray proton escape time Cosmic-ray production rate can be calculated from synchrotron luminosity of relativistic electrons

  21. Starburst Contribution to the Gamma-Ray Background Thompson, Quataert, & Waxman 2006

  22. Cosmic Background of High-Energy Neutrinos AMANDA, ANTARES, NESTOR IceCube, NEMO, ANITA Loeb & Waxman, astro-ph/0601695

  23. The predicted neutrino background at is implying a detection rate of in a terrestrial detector like IceCube neutrinomuon in Antarctica iceCerenkov lightoptical sensors

  24. Conclusions • Collisionless IGM shocks accelerate electrons and protons to relativistic energies. • The gamma-ray (IC) and radio (synchrotron) emission by the accelerated electrons could be a substantial fraction of the fluctuations in the low-frequency (<10 GHz) and gamma-ray backgrounds. • X-ray clusters are radioandgamma-ray clustersas well • Starburst galaxies are efficient factories of high-energy gamma-rays and neutrinos.

  25. ? The radio sky total CMB ERB estimates Galactic synchrotron IGM shocks ν [MHz] Keshet, Waxman & Loeb (2004b) IGM: significant fraction of ERB

  26. Fluctuations for ℓ=400⇔θ=00.5 LOFAR IGM shocks Galactic synchrotron ∝ℓ-1/2 ~ const for 400<ℓ<4000 discrete sources ∝ℓ 21 cm tomography CMB Bremsstrahlung from Lyα clouds 1’-00.5: IGM fluctuations dominate Keshet, Waxman & Loeb (2004b)

  27. Future radio telescopes LOFAR SKA Northern Netherlands shore

  28. Physical Conditions: Arp 220 HST Nicmos Image LFIR ~ 1012 L Double Nuclei ~ 350 pc apart 2 ~ 100 pc scale disks with ~ 109 Mgas (+ circumbinary disk) gas ~ 10 g/cm2 ~ 4000 MW (optically thick to FIR) <n> ~ 104 cm-3 vs. <n>MW ~ 1 cm-3 Sakamoto et al. 1999

  29. Surface Densities actual B minimizing energy-B Thompson et al. astro-ph/0601626

  30. Synchrotron Emission by Secondary GeV emit at a synchrotron frequency of ~1GHz (B/0.1mG) and cool faster than the starburst lifetime (Thompson et al. 2006) The local 1.4GHz energy production rate per unit volume in starbursts implies

  31. Cumulative Synchrotron Luminosity Density Yun, Reddy, & Condon 2001

  32. Extrapolation to Neutrino Energies >>GeV In analogy with the Milky-Way power-law distribution of protons where s=0.5-0.6 characterises the confinement time An injection index of -2 is expected for Fermi acceleration in strong shocks If starbursts are characterized by the MW injection index then up to the “knee” at ~0.1PeV or higher

  33. UHECRs • Present-day energy production rate of relativistic protons in starburst galaxies is comparable to the energy production rate of ultra high-energy cosmic-rays, potentially because the former applies to and the latter to , with the two matching at

  34. ν Iν 10-11 10-12 ν MHz GHz THz { 100 MHz 10 1 00.1 10 Radio signal Model & simulation agree well Keshet, Waxman & Loeb (2004b)

  35. Previous estimate (Sreekumar et al. 1998) 70% syn (22 GHz) 30% gas (21 cm) North North South South EGRB: lower than previously thought EGRB upper limit: 1/3 of previous estimate Keshet, Waxman & Loeb (2004a)

  36. Different, sometimes conflicting Osborne,Wolfendale and Zhang (1994) Sreekumar et al. (1998) Correlations with tracers results recovered sensitive to tracer sensitive to region Model uncertainties cosmic ray distribution optical, IR fields magnetic field Latest study (Sreekumar et al. 1998) above polar non-isotropic correlated Previous EGRB estimates Previous estimates problematic Keshet, Waxman & Loeb (2004a)

  37. M=4 adiabaticity entropy changes indicate shocks M 100 103 102 101 104 100 10-2 10-1 10-3 10-4 Shock Identification Efficient shock extraction from SPH Keshet et al. (2003)

  38. ξe=5% GLAST EGRET model Fε∝faccfT ξe GLAST 3σ correlation: Abell clusters & EGRET flux (Scharf & Mukherjee 2002) Launch: 2007 Detecting γ-ray signal fr<δ2Iν(θ)>1/2/<Iν> 100 N(>F) IC Waxman & Loeb 2000 10-1 10-1 100 θ/fr F[ph s-1 cm-2] Dozen GLAST sources for ξe=3% Keshet et al. (2003); Keshet, Waxman & Loeb (2004b)

  39. J ∝ ξefacc fT model 100 J ∝ ξe 10-1 ε2dJ/dε[keV s-1 cm-2 sr-1] 10-2 ε[eV] 10-3 GeV MeV keV Keshet, Waxman & Loeb (2004b) Inverse-Compton spectrum simulation J ∝ ξe Keshet et al. (2003) Simulation and model agree!

  40. ? ๏ Asymmetry important for radio Keshet, Waxman & Loeb (2004b) Radio signal: fr ?

  41. γ-rays 1. >Several GLAST clusters if ξe>3% 2. Resolved clusters with Ćerenkov detectors 3. Statistical detection(possibly with EGRET, Scharf & Mukherjee 2002) Radio 1. SKA and LOFAR: 2. Possible detection (VLA, LF CMB) by LSS correlations 3. Very low frequency (<20 MHz) Galactic features √ Model + SPH algorithm for IGM shocks √ Extragalactic backgrounds: EGRB low, ERB indirect Quantitative predictions for emission from IGM shocks, testable in the next few years Conclusions

  42. GC NGC NAS L-I NGP Rule out direct ERB identification Important Galactic features Galactic LF radio sky Keshet, Waxman & Loeb (2004b)

  43. Gamma Ray Large Area Space Telescope • Launch in 2007 • 20 MeV to 300 GeV • Wide-field imaging telescope • NASA cost is $326 M • http://glast.gsfc.nasa.gov/ Theme:Exploring Sites of Particle Acceleration in the Universe

  44. Energy Range Energy Resolution (DE/E) Effective Area (peak) Field of View Angular Resolution Sensitivity (> 100 MeV)* Mass Lifetime * 2 year survey at high latitudes AGILE 30 MeV - 50 GeV 1 700 cm2 ~ 3 sr 4.7° @ 00 MeV 0.2° @ 10 GeV 5  10-8 cm-2 s-1 60 kg 2002 - 2005 EGRET 20 MeV - 30 GeV 0.1 1500 cm2 0.5 sr 5.8° @ 100 MeV 0.5° @ 10 GeV ~ 10-7 cm-2 s-1 1810 kg 1991 - 1997 GLAST 20 MeV - > 300 GeV 0.1 12000 cm2 2.5 sr ~ 3.5° @ 100 MeV ~ 0.1° @ 10 GeV ~ 2  10-9 cm-2 s-1 3000 kg 2005 - 2010 Mission Parameters

  45. Number of Extended Sources

  46. Results Based on a Numerical Simulation of Structure Formation in the IGM Uri Keshet, Waxman, Loeb, Springel, & Hernquist 2002